If a web app is run from the iOS 4.3 home screen – in other words, if
it is saved to the screen alongside local apps downloaded from the
Apple App Store – and launched into full-screen mode, it runs roughly
two to two and a half times slower than it does in the browser,
according to various tests. It appears that whereas Apple has updated
the iOS 4.3 Safari browser with its high-speed Nitro JavaScript
engine, Nitro is not used when web apps are launched from the home
screen.